To examine the effect of resistive loading on variational activity of breathing, we studied 18 healthy subjects breathing at rest and with inspiratory resistive loads of 3 and 6 cm H2O/L/s, applied randomly for 1 h each. Compared with resting breathing, a resistive load of 3 cm H2O/L/s decreased the ...

There is presently considerable ambiguity and confusion relating to ventilator terminology. This can be eliminated using a simple approach, visualising mechanical ventilation as an inspiratory pump, and defining trigger, limit, and cycling in this context. The trigger is the signal that starts a breath by opening the inspiratory valve, the ...

We compared qualitative and quantitative aspects of perceived exertional dyspnea in patients with interstitial lung disease (ILD) and normal subjects and sought a physiological rationale for their differences. Twelve patients with ILD [forced vital capacity = 64 +/- 4 (SE) %predicted] and 12 age-matched normal subjects performed symptom-limited incremental cycle ...

We subjected 29 healthy young women (age: 27 +/- 1 yr) with a wide range of fitness levels [maximal oxygen uptake (VO2 max): 57 +/- 6 ml . kg-1 . min-1; 35-70 ml . kg-1 . min-1] to a progressive treadmill running test. Our subjects had significantly smaller lung volumes ...

Although the esophageal stethoscope has been used for many years, the effect of the depth of placement on the quality of the sounds obtained has never been investigated. The amplitude and frequency characteristics of the first and second heart sound and of inspiratory and expiratory breath sounds were determined at ...

(Abstract) <p>BACKGROUND. Previous research has shown that the ventilatory threshold (VT) correlates highly with onset of lactate accumulation and maximal steady-state exercise (MSS) level. Also, studies have shown the VT is useful in prescribing exercise for cardiac patients in that it gives an exercise intensity at which the patient is ...

The presence of abnormalities of the respiratory center in obstructive sleep apnea (OSA) patients and their correlation with polysomnographic data are still a matter of controversy. Moderately obese, sleep-deprived OSA patients presenting daytime hypersomnolence, with normocapnia and no clinical or spirometric evidence of pulmonary disease, were selected. We assessed the ...

The purpose of this study was to determine the effects of different inspiratory resistances on exercise performance and to describe physiological and subjective responses during constant load work of an intensity that elicits the maximum sensitivity to respiratory factors of respirator wear. Nine subjects (mean age 25.8 +/- 4.8 years) ...

The anesthetist will get the most information out of a capnograph if it is examined systematically. First, the anesthetist must determine whether exhaled CO2 (i.e., a waveform) is present. The differential diagnosis of absent CO2 includes esophageal intubation, accidental tracheal extubation, disconnection of the breathing circuit, complete obstruction of the ...

BACKGROUND: The purpose of our investigation was to assess the use of a fixed value (12-13) of the Rating of Perceived Exertion (RPE) scale (6-20) as a valid method for the determination of the workload corresponding to the ventilatory threshold (VT) during a ramp protocol on a cycle ergometer. METHODS: ...

The application of negative expiratory pressure (NEP) at end expiration has been shown to cause reflex-mediated activation of the genioglossus muscle in awake humans. To test whether a reflex contraction of pharyngeal dilator muscles also occurs in response to NEP applied in early expiration, the effect on genioglossus muscle reflex ...

The effects of 8 wk of inspiratory resistive loading (30 min/d, 3 x/wk) on diaphragm mass, contractile properties, fatigue, and fiber dimensions were studied in 10 male Wistar rats. They were conditioned to breathe through a Hans-Rudolph device. Half of them had to overcome a moderate inspiratory resistance (MR; n ...

In utero hypoxia may affect the development of the brain and result in altered respiratory responses postnatally. Using a barometric plethysmograph, we examined the effects of exposing pregnant guinea pigs to 200 ppm carbon monoxide (CO) for 10 h/d from d 23-25 of gestation until term (approximately 68 d) on ...

BACKGROUND AND PURPOSE: Despite the arms being used extensively in the performance of many occupational tasks, little is known about the pattern of breathing and physiological cost of such work. The purpose of this study was to establish whether a simple change in arm support could alter the workload, pattern ...

There is very little information about the effect of inspiratory muscle training on inspiratory flow (V'I) and thus on power output (PO) in patients with chronic obstructive pulmonary disease (COPD). In this study we aimed to evaluate the changes induced by training on the determinants of PO. Thirty one patients ...

The aim of this mixed cross-sectional longitudinal study covering a total age range of 11-17 years, i.e. the entire pubertal growth period, was (1) to specify the changes in maximal breathing pattern during incremental exercise; (2) to determine what parts of the changes are due to anthropometric characteristics, physical fitness ...

The forced expiratory manoeuvre was first described by Tiffeneau and Pinelli working in Paris (France), in December 1947, who proposed measurement of the "pulmonary capacity usable on exercise" (capacité pulmonaire utilisable à l'effort) (CPUE), the maximal volume expelled in one second after a deep inspiration. It was intended to replace ...

The development of fatigue was investigated in the diaphragm of anaesthetized, tracheostomized, spontaneously breathing cats during restricted air flow. Ventilation, transdiaphragmatic pressure (Pdi), integrated electrical activity of diaphragm (Edi) and phrenic nerve (Eph) were measured simultaneously and expressed as a percentage of values at unloaded breathing. Inspiratory loads were 60, ...

Multiple mechanisms have been proposed to explain the hyperventilation and the limited exercise capacity in congestive heart failure (CHF) including increased intrapulmonary pressures, total pulmonary resistance, and airway abnormalities. We investigated the hypothesis that inhalation of nitric oxide could influence the maximum exercise capacity and excessive ventilatory response to exercise ...

During exercise, large pleural, abdominal, and transdiaphragmatic pressure swings might produce substantial rib cage (RC) distortions. We used a three-compartment chest wall model (J. Appl. Physiol. 72: 1338-1347, 1992) to measure distortions of lung- and diaphragm-apposed RC compartments (RCp and RCa) along with pleural and abdominal pressures in five normal ...

STUDY OBJECTIVE: The purpose of this investigation was to compare multiple ventilatory responses of heart transplant patients (HTP) with normal subjects (NL) at rest, at absolute and relative submaximal exercise levels, and at peak exercise. DESIGN: Ten male HTP and 10 matched NL were tested under similar conditions on a ...

The purpose of this study was to examine blood lactate (BLa) levels and ratings of perceived exertion (RPE) in nine boys (10.5 +/- 0.7 yr) and nine men (25.3 +/- 2.0 yr) during exercise relative to ventilatory threshold (VT). VT and VO2max were determined during a graded exercise test on ...

We examined the hypothesis that O2 uptake (VO2) would change more rapidly at the onset of step work rate transitions in exercise with hyperoxic gas breathing and after prior high-intensity exercise. The kinetics of VO2 were determined from the mean response time (MRT; time to 63% of total change in ...

Inspiratory muscles are weak and contribute to exercise limitation in chronic obstructive pulmonary disease (COPD). Differential inspiratory pressure contributions from the diaphragm and inspiratory rib cage muscles (RCMs) during exercise in patients with COPD patients are insufficiently described. We measured, in 16 patients with COPD, the global inspiratory muscle pressure ...

To investigate the role of high frequency oscillation (HFO) in promoting meconium clearance from the airway, we used a commercially available ventilator configured with maximal expiratory flow exceeding inspiratory flow (asymmetric HFO or AHFO). We hypothesized that AHFO would move meconium in an expiratory direction (toward the ventilator). We first ...

Nine healthy subjects (age 31 +/- 4 yr) exercised with and without expiratory-flow limitation (maximal flow approximately 1 l/s). We monitored flow, end-tidal PCO2, esophageal (Pes) and gastric pressures, changes in end-expiratory lung volume, and perception (sensation) of difficulty in breathing. Subjects cycled at increasing intensity (+25 W/30 s) until ...

Phrenic motoneuron firing rates during brief inspiratory resistive loading (IRL) are high, and nearly all the motoneurons are recruited. Diaphragmatic fatigue has been difficult to demonstrate during IRL. Furthermore, evidence from studies in limb muscles has shown variable motoneuron responses to prolonged high-intensity loads. We studied phrenic motoneuron firing rates ...

We compared the effects of two step durations on breathing pattern, mouth occlusion pressure and "effective" impedance of the respiratory system during incremental exercise. Nine normal subjects (mean age: 27.8+/-1.21 years) performed two incremental exercise tests in randomized order: one test with step increments every 1 min 30s and the ...

This study was designed to compare the bronchodilatatory effect of terbutaline inhaled through Turbuhaler (TH) or pressurized metered-dose inhaler (pMDI) in young asthmatics, and to assess the possible relationship between patients' inspiratory capacity and bronchodilatation for both devices. One hundred and eighteen asthmatics (aged 4 10/12-20 6/12 years) with bronchial ...

PURPOSE: The standard conditions of spirometry (i.e., wearing a noseclip and breathing through a mouthpiece and a pneumotachograph) are likely to alter the ventilatory pattern. We used "time motion" mode (M-mode) sonography to assess the changes in diaphragm kinetics induced by spirometry during quiet breathing. METHODS: An M-mode sonographic study ...

How the effects of frequency, tidal volume (VT) and PEEP interact to determine the mechanical properties of the respiratory system is unclear. Airway flow and airway and esophageal pressures were measured in ten intubated, anesthetized/paralyzed patients during mechanical ventilation at 10-30 breaths/min and VT of 250-800 ml. From these measurements, ...

We studied 134 patients with Steinert's myotonic dystrophy (MD) in order to determine the prevalence of chronic hypercapnia, the level of muscle weakness and forced expiratory volume at which hypercapnic respiratory failure is likely to occur, and how clinical assessment might help predict hypercapnic respiratory failure. Subjects were divided into ...

We prospectively assessed whether baseline central hemodynamics and exercise capacity can predict improvement of VO2 at ventilatory threshold (VT) after exercise training in patients with severe chronic congestive heart failure. Eighteen patients (mean +/- SEM; age 52 +/- 2 years), half of them listed for transplant, underwent 3 weeks of ...

Improved ventilation and exercise capacity follows thoracoscopic lung volume reduction surgery (TLVRS) in patients with severe emphysema. This improvement could be related to changes in inspiratory and expiratory flows following surgery, with consequent improvement in dyspnea indices. Changes in inspiratory/expiratory flows at rest and exercise and their relation to subjective ...

OBJECTIVE: The purpose of this investigation was to study the relationship between the lactate (LT) and the ventilatory threshold (VT) during a ramp protocol in cycle ergometry. PARTICIPANTS: Thirty nine trained male subjects were selected as subjects. EXPERIMENTAL DESIGN: All the subjects performed a maximal ergometric test on a cycle ...

Task failure during inspiratory resistive loading is thought to be accompanied by substantial peripheral fatigue of the inspiratory muscles. Six healthy subjects performed eight resistive breathing trials with loads of 35, 50, 75 and 90% of maximal inspiratory pressure (MIP) with and without supplemental oxygen. MIP measured before, after, and ...

The purpose of this study was to investigate the possible use of integrated surface electromyography (iEMG) in cardiac transplant patients (CTPs) as a new noninvasive determinant of the metabolic response to exercise by studying the relationship between the iEMG threshold (iEMGT) and other more conventional methods for anaerobic threshold (AT) ...

The genioglossus is an upper airway dilator muscle, the length of which is directly related to patency in the oropharyngeal region. We hypothesized that genioglossal length (Lgg) is dynamically influenced by the afterload exerted by negative upper airway pressure during inspiration and by the intrinsic length-tension characteristics of the muscle ...

Several indices of ventilatory heterogeneity can be identified from the expiratory CO2 partial pressure or CO2 elimination versus volume curves. The aims of this study were: 1) to analyse several computerizable indices of volumetric capnography in order to detect ventilatory disturbances; and 2) to establish the relationship between those indices ...

Instantaneous respiratory effective elastance (Eteff) and tissue resistance (Rt) may be measured by studying the relationship between flow at the airway opening and at the chest during forced oscillations; using that method it has been shown that Rt varies little during breathing while Eteff presents much larger phasic variations than ...

The onset of anaerobic (lactate) metabolism during incremental exercise, which may be a result of an imbalance between tissue oxygen supply and demand, has been associated with the gas exchange ventilatory threshold (VT). This study was designed to examine whether near infrared spectroscopy (NIRS) could be used to detect the ...

The effect of inspiratory muscle training (IMT) on exercise capacity in patients with chronic airflow limitation (CAL) has been debated. The present study was planned to further investigate the effects of IMT on exercise performance. Twenty patients (aged 62+/-1 yrs; forced expiratory volume in one second/forced vital capacity (FEV1/FVC) 36+/-2%) ...

This study evaluated the effects of varying tidal volumes (VT) and positive end-expiratory pressure (PEEP) levels on surfactant aggregate conversion and lung function in an animal model of lung injury induced by N-nitroso-N-methylurethane. Lung-injured adult rabbits were initially ventilated using a VT of 10 ml/kg (VT10), a respiratory rate of ...

Cross-sectional studies have indicated that the pattern of ventilatory responses to exercise evolves during the course of childhood. This 5-year study was designed to provide a longitudinal assessment of minute ventilation (VE), tidal volume (VT), and breathing frequency (fR) in 20 children (11 girls, nine boys) between the ages of ...

Patients with chronic obstructive pulmonary disease have abnormal breathing and ventilatory muscle recruitment patterns at rest and during exercise, and these alterations may contribute to the limited exercise capacity seen in this disease. Lung volume reduction surgery (LVRS), a recently described treatment for emphysema, is reported to improve exercise performance. ...

In adolescent idiopathic thoracic scoliosis (ITS) working capacity may be reduced during exercise. Despite concern about its usefulness, bracing is still being used in ITS. Thus the effects of bracing on exercise performance need to be examined. We studied six females, ages 12-15 years who had mild ITS (Cobb angle ...

The aim of this study was to determine how Wavelet transform analysis of signal-averaged ECGs can identify patients with conduction defects who are at high risk for development of ventricular tachycardia. In this study, 34 SA-ECGs and programmed electrical stimulation (PES) reports were obtained from the OSU Department of Cardiology ...

The aims of the present study were: (1) to assess aerobic metabolism in paraplegic (P) athletes (spinal lesion level, T4-L3) by means of peak oxygen uptake (VO2peak) and ventilatory threshold (VT), and (2) to determine the nature of exercise limitation in these athletes by means of cardioventilatory responses at peak ...

We compared qualitative aspects of the sensory experience of exertional breathlessness in normal subjects and in patients with chronic airflow limitation (CAL) and sought a physiologic rationale for these. Twelve patients (66 +/- 2 yr of age, mean +/- SEM) with severe CAL (FEV1 = 37 +/- 5% predicted) and ...

The present study was performed to examine whether or not the ventilatory response at the onset of voluntary exercise and passive movement in endurance runners is the same as in untrained subjects. Twelve long-distance runners belonging to the varsity athletic club and 13 untrained subjects of our university participated as ...